Process of making cyanids



7 'Aug. 28, I923. 1,266,627

. K. P. MGELROY PROCESS OF'MAKING CYANIDS Filed Jan. 25. 1922 2Sheets-Sheet l VIP wi Aug. 28, 1923. 1,466,627 K. P. MCELROY PROCESS OFMAKING CYANIDS Fiied Jan. 25, 1922 2 Sheets-Sheet 2 [Mam/Ira? i P; M maPatented Aug. 28, 1923.

UNITED STATES PATENT OFFICE.

KARL P. MOELROY, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO FERROCHEMICALS INC., OF WASHINGTON, DISTRICT OF COLUMBIA, A CORPORATION OFDELAWARE.

I PROCESS OF MAKING CYANIDS.

Application filed January 25, 1922. Serial No. 531,614.

To all whom it may concern: Be it known that I, KARL POMERY MoEL- ROY, acitizen of the United States residing at \Vashington, in the District ofColumbia, have invented certain new and useful Improvements in Processesof Making Cyanids, of which the following is a specification.

This invention relates to processes of making cyanids; and .it comprisesa method wherein cyanid forming materials are fed to a suitable reactionchamber in which a dominant mass or pool of cyanid in the liquid and thevapor phase is maintained by aid of heat supplied by electrical means,the temperature being maintained above 1000. C. and cyanid being removedand recovered from the sphere of reaction as liquid or as vapor; all asmore fully hereinafter set forth and as claimed.

The present invention is in part based upon a discovery that attemperatures above 1000 C. cyanid reacts with oxidized forms of alkalito form carbon monoxid, setting free nitrogen and alkali metal and thatin making cyanid, the initial presence of cyanid itself in substantialproportions accelerates the conversion of alkali to cyanid in thepresence of carbon and nitrogen. I have found that in systems comprisingalkali, cyanid, carbon, nitrogen and carbon monoxid the conversion ofalkali to cyanid is accomplished with what may be termed commercialvelocity when the alkali and cyanid are present as vapor in substantialconcentrations in the gas phase of the syS-.

tem, that is, at temperatures ranging above 1000 C. at about one or twoatmospheres pressure.

Alkali, carbon and nitrogen when heated together form cyanid. Thereaction is highly endothermic and most of attempts which have been madeto utilize it technically have failed because of the inherent difficultyof supplying heat for the reaction -for the tendency of c anid to revertto alkali in presence of C at temperatures below those at which cyanidis formed.

In a copending application Serial No.

477,205, filed June 13, 1921, I havedescribed I and claimed a process ofmaking cyanid from alkali, carbon and atmospheric nitrogen wherein thesematerials are heated together to a temperature well over 1000 C. lI1 ablast furnace such as is used for making pig iron, the operation of thefurnace being so regulated that a dominant mass or pool of cyanid liquidand vapor is maintained in thehot zone of the furnace, the alkali beingfed to such pool and cyanid removed therefrom at a rate proportioned tothe supply of heat thereto. In the invention which is the subject matterof said application the source of heat used is the combustion ofpreheated carbon under gas producing conditions (that is to carbonmonoxid) with preheated air, said combustion taking place in or inproximity to said dominant pool of cyanid. In said application thereinforcement of the combustion heat by electricall developed heat isdescribed but not claime concentration of cyanid vapor is possible inthe gases produced; the cyanid producing capacity of a furnace of givensize being substantially increased over that which is possible whengasification of carbon with air constitutes the main supply of heat.

Since sodium cyanid is now the standard commercial form of cyanid andsince sodium carbonate (soda ash) on account of its cheapness and itscomposition is an advantageous source of alkali for making cyanid, Ishall describe the invention with particular reference to making sodiumcyanid from sodium carbonate, it being understood,

that the invention is applicable to the pro-v duction of any othercyanid. I may use as the alkali of the process the oxid or carbonate (orcompound capable of yielding these), of any alkali or alkaline earth oreven the alkali or alkali earthmetals themselves and produce thecorresponding metal cyanid.

For example potash, baryta, strontia, lithiav or even thallia areavailable in this connecrepresented by the reversible reaction Thechemical energy involved in this reaction is, according to generallyaccepted data on heats of formation, 134320 calories, plus or minus.This quantity of heat is absorbed in the formation of cyanid fromcarbonate or is set free in the reversal of the reaction. The reactioncomes to an equilibrium with a ratio of cyanid to carbonate dependingpartly upon the relative concentrations in the system of nitrogen andcarbon monoxid and partly upon the temperature. Above 1200 C. cyanid ispractically 100 per cent stable in the presence of ()0 alone and theconversion of carbonate to cyanid, with substantial proportions ofinitially present cyanid, takes place quickly and completely. From thepractical standpoint therefore, the production of cyanid becomes amatter of an adequate supply of heat available for the reaction atatemperature around 1200 C. Since at these temperatures the vaporpressure of cyanid is quite large the cyanid formed is to a great extentin the vapor phase and heat for vaporization is required in addition tothe heat of reaction. The total work of converting carbonate, carbon andnitrogento cyanid vapor at 1200 may be estimated to be, (per moleculeNaCN):

Calories. 67160 23000 Heat absorbed in reaction Sensible heat of NaCN at1200 Latent heat of fusion and vaporization 34500 Sensible heat 1%molecules CO 13400 The semi-combustion of carbon to form carbon monoxidevolves only about 30 per cent of the total heat of combustion of carbonbut this amount is suflicient to raise all of the products of combustionto 1200 C. and leave a margin over available for making cyanid; that isfor heating a certain further amount of carbon up to this temperatureand producing cyanid from it. The greater the preheat which can be givenair and carbon the greater is this margin; and contra, the greater theheat losses by radiation and the like, the less the margin. Radiationlosses are proportional to temperature, time and area of exposedsurface, and the faster the semi-combustion can be driven and the largerthe furnace unit, the less the percentage loss of heat in this way. Inlarge apparatus like a blast furnace or a big gas producer, usingpreheated blast and preheated fuel (see application Serial No; 477,205)the gasification of carbon with air may theoretically be as low as 0.3to 0.5 pound per pound of cyanid produced in the gases in the vaporform. With lower tem- Y peratures giving slower reaction and withsmaller apparatus, the figures are not so favorable. I

In the yield just mentioned, the cyanid is in the vapor form and thisrepresents an expenditure of heat which, if the cyanid were delivered asliq'uid, would be available for the production of more cyanid. In theproduction of cyanid by semi-combustion of carbon with air as a sourceof heat, of necessity a large volume of gases is produced; this gasbeing carbon monoxid from the carbon and from the alkali carbonate andunused nitrogen. As sodium cyanid has a high vapor tension at 1200, withthis bulk of gases the product exists in the vapor form. With a. lessvolume of gases, more or less of it occurs in the liquid form with aconcomitant decrease in the amount of heat needed for cyanidation.

In one embodiment of the present invention I maintain a highconcentration of cyanid vapor in the gases roduoed in the hearth orcombustion zone oi a blast furnace or slagging gas producer byreinforcing the combustion heat by heat electrically developed in saidzone. At the same time I so proportion the feed of alkali to the furnaceand the withdrawal of gases at a low point in the furnace to the supplyof heat to said hot zone that a dominant pool of cyanid, as liquid andvapor, is established and maintained therein, as more fully described inmy application Serial No. 47 7 ,205. In so doing, the production ofcyanid is smooth and regular and the capacity of a given furnace isincreased over that which ispossible when combustion heat alone is used.Furthermore in working thus, the production of cyanid in a relativelysmall sized furnace becomes profitable whereas in very small furnaces,using combustion heat alone, the radiation and cooling factor is of suchweight that the concentration of cyanid vapor in the gases may be smalland the time yield concomitantly low. The proportion of combustion heatto electric heat may be as desired. I usually find it advantageous, onaccount, of the relative costs of combustion heat and electric energy,to have the proportion of combustion heat large and to apply electricenergy in quantity sufficient merely .to overcome heat losses, therebvmaintaining a high concentration of cyanid vapor without unduly' fastdriving. ut I may in some cases rely principally upon electrical heatingand make the combustion heat of subordinate weight, merely passing airinto the reaction zone at a. rate sufiicient to maintain an excess ofnitrogen therein. In one embodiment of the invention hereinafterdescribed. I may use electrical heat alone and I may even pass nitrogeninstead of air or mixed with air into the reaction zone. In thisembodiment part of the cyanid is removed from the reaction zone in theliquid state, the use of electric heat serving to keep the volume ofgases, and thereby the vaporization of cyanid, at a minimum.

In recovering cyanid from gases carrying it by condensing the vapor anddepositing fume it is desirable to quickly cool such gases so as to passrapidly through the temperature range at which cyanid tends to revert toalkali in the presence of CO and.

in this connection it makes for economy to have the concentration ofcyanid vapor high and that of other gases low. When using electricalheat as above described, the temperature of the reaction zone maybe -controlled independently of the speed of gas flow. The predominance ofcyanid in the reaction zone is secured by this temperature control whichresults from proportioning the input of electric energy to the feed ofcyanid forming materials going to the reaction zone and the withdrawalof cyanid and heated gases therefrom. The temperature is advantageouslyabove 1000'C. and it is advantageous to keep it about 1200. In usingfuels with high ash as a source of carbon it is advisable to run at anash-slagging temperature with addition of lime, or other suitable flux,and the temperature may then be from 14009 to 1500; the gases may inthis case be taken from the reaction chamber at lower temperatures.

The application of electric heat to the cyanid forming reaction zone .isaccomplished by any suitable or convenient means.

In a shaft furnace provided with tuyeres near the bottom for blowingwith hot air.

and with outlets for hot gases above the bosh or fusion zone, currentmay be supplied to the hot zone by meansof electrodes placed in suitableapertures through the furnace walls, the furnace charge, comprisingcharcoal or coke impregnated with cyanid and alkali serving asresistance material. Or the slag bath in the bottom of the furnace maybe used as resistor, heat electrically generated therein radiatingupwardly to the reaction zone. Or an electric furnace ofthe arc typewith multiphase currents may be used, such furnace being provided withtuyeres for admission of hot air and having a superimposed shaft throughwhich a regulated proportion of the cyanid laden gases from the hot zonepasses upward in counter-current to a descending charge of alkalizedfuel, and cyanid being condensed and recovered from a portion of saidgases which are led from the furnace while they are at a temperatureabove 1000 and quickly cooled or otherwise treated for the separa tionof cyanid. A convenient method for supplying electric heat is by meansof eddy currents induced in suitably prepared conducting liningsprovided in the hot zone, this zone being surrounded by heat insulatingmaterial and, outside of this, by a coiled electric conductor carryinghigh frequency alternatingcurrent. This method of apply-,

ing electric heat is of particular advantage with a small slagging gasproducer Where it may be desirable merely to compensate losses byelectrically developed heat and where the heat of gasification ofpreheated carbon with preheated air may be relied upon for the greaterproportion of the necessary heat supply to the hot zone. The inductionmethod may however also be conveniently utilized in a shaft furnaceWhere electric energy is the main source of heat, that is, wherecombustion heat is only incidental and considered merely as lesseningthe heat requirement of the cyanidreaction. It may here be noted thatthe use of air is usually preferable to that of nitrogen alone and thatenrichment of the air with oxygen also makes for energy economy.

In the drawings annexed hereto I have shown, more or lessdiagrammatically, certain apparatus elements within the presentinvention and adapted for use in the opera tion of thedescribed method.

Fig. 1 is a view in central vertical section of an induction furnace;

an arc-heated the lining of the furnace. This is made of electricconducting material such as nichrome or other suitable refractory metalor it may be of graphitized carbon impreg.' nated and coated internallywith magnesia or other suitable material. 5 represents a water cooledelectrical conductor with electrical leads 6 carrying high frequencyalternating currents by means of which heating currents are induced inthe carbon cylinder 4 and in the alkalized and cyanized carbon which isin the furnace. The furnace is charged with material at the to by meansof the charging hopper and bell The cylinder 4 isheat insulated by thematerial 8 consisting preferably of lamp black which is held in place bythe casing 9 made of micanite or other electrical insulator. As shown,the bottom of the cylinder is inclined leads 15.

downwardly from the gas outlet toward the cyanid hole 3.

Fig. 2 depicts an electric resistance furnace in which the charge ofalkalized and cyanized carbon constitutes the resistor. Elements 10 areair inlets, 11 the gas outlets, 12 the outlet for removal of moltenmaterial and 13 is a small carbon rod for carrying the starting currentbetween the electrodes 14, supplied with current through electrical Thefurnace is fed with alkali and carbon through the charging devices 16provided, as shown, with bells and hoppers. The furnace as shown isbuilt with a flare or increasing cross sectional area toward the bottomso as to decrease the electrical resistance of this part of the chargeand concentrate the heating effect of the current toward the top. Thecasing 17 may be made of magnesite or chromite brick work or of othersuitable material. The conduit 18 carries cyanid laden gases toapparatus for recovery of cyanid, which may be such as that shown inFig. 4.

Fig. 3 shows a furnace of the blast furnace type provided with bustlepipe and tuyeres 20 as air inlet, hot gas outlets 21,

- metal and slag outlet 22, and cool gas outlet 23 near the top.Inserted in the bosh walls through water cooled openings are electrodes24 with electrical leads 25. The furnace has the usual charging device26. The hot gas outlets 21 lead into an annular conduit 27 which isconnected by conduits 28 to apparatus for cyanid recovery, here shown ascomprising a water jacketed condenser 29 containing cooling pipes 30.This is a type of apparatus adapted for quickly cooling the hot cyanidladen gases through the temperature range below 1000, in which cyanid inpresence of CO tends to revert to oxid and carbonate. Valves 31 and 32are for the purpose of regulating the relative proportions of thefurnace gases leaving the furnace through hot gas outlets 21 and passingup through the shaft and out by cold gas outlet 23.

Figure 4 shows another type of apparatus for quickly cooling cyanidladen gases; which may be used in connection with any of the furnacesherein described, being for example connected by inlet 35 to outlet 28of the structure of Fig. 3 to outlet 18 of Fig. 2 or outlet 2 of Fig. 1.In this showing, inlet 35 is a conduit leading from the hot gas outletof any cyanid furnace. Elements 36 and 37 are sheet metal towersconnected at the bottom by conduit 38 and connected at the top byconduit 39. Conduit 38 is in the form of a hopper with a U-shapedbottom. In tower 37 are shown cooling pipes 40 in which air, water orother cooling medium circulates. Through the conduit 38 runs theconveyor 41 delivering into receptacle 42.

A thermal circulation of gases may be mainaaeaeav culation upwardly in36 and downwardly in The 37. Cyanid is quickly condensed in 36, falls tothe bottom and is removed by conveyor 38. As condensation is favored bynuclei, dustlike suspended particles are built up until they are largeenough to fall freely.

The apparatus therefore gives or may be made to give, a granularproduct. Excess of gas passes out through pipe 43. Control of the volumeof gas passing out of the apparatus and, therefore, of the volume of hotgas entering, is secured by adjustment of valve 44. A pyrometer 45indicates the temperature resulting from the mixture of incoming hot gaswith the mass of gas maintained in 36. The mass of hot gas which anapparatus of this type can handle is a matter of design. Usually thecirculation through the towers is sufiiciently rapid without the aid ofa fan in conduit 39, but such a fan (not shown) may be used. There maybe as many of these coolers connected to the hot gas outlet of a.furnace as are required to handle the volume of hot gas required to betaken from the furnace in securing'the desired regulation thereof asdescribed.

The apparatus of Figs. 1 and 2 are worked similarly. They differ mainlyin the means provided for applying electric energy. Being filled withalkalized carbon in lumps (which may be charcoal, coke or other form ofcarbon impregnated with soda) the electric current is applied and thefurnace brought When the alkali in-the furnace is .cyanided,

which can be tested by withdrawing a sample through 3 or 12, the airvolume is increased and the feed of alkalized carbon through 7 or 16 iscorrelated with the air volume, both being properly proportioned withregard to the electric energy applied, thereb maintaining thetemperature at the desire degree. The gases leaving the furnace through2 or 11 now carry cyanid vapor in concentrations (below the saturationpoint) depending upon the ratio between the electric energy applied andthe heat of combustion. .The latter is a function of the speed ofdriving (the volume of air per minute with the correlated alkali andcarbon feed). With the speed of driving fixed the concentration ofcyanid vapor in the gases varies directly with the electric alkali fedover that suflicient to saturate the gas as it leaves the furnacecollects as cyanid in the molten state at the bottom of the furnace andis drawn ofi' from time to time through 3 or 12. The collectionof liquidcy-,

anid in this way is aided by the flare of the furnace shown in Figure 2and by placing the induction coil 5 on the furnace of Fig;

1 well above the bottom, thus providing for a cooling effect and causinga condensation of cyanid from the gases before they leave the furnace.It is advisable with this type of furnace to keep the temperature at aminimum consistent with adequate speed 'of cyanid formation, thusminimizing heat con-- sumption and recovering in the molten state asdescribed the maximum proportion of the cyanid formed in the furnace.

In the operation as above described I am in effect continuouslygasifying carbon by sodium carbonate and by air, maintaining atemperature at which soda is vaporized and, in mixture with nitrogen andcarbon monoxid, the soda vapor is contacted with carbon thereby formingcyanid, the conversion being accelerated by maintaining in the reactionzone substantial quantities of preformed cyanid serving as a dominantpool. With sufficiently fast driving, carbon dioxide may be first formedin the upper zones of the furnace, the heat of CO formation beingpartially absorbed in vaporization of soda; the soda vapor and COtogether'with nitrogen, all at a'very high temperature, subsequentlycontact with carbon to form cyanid and CO with a drop in temperature asthe gases proceed through .the reaction zone, Thev size of this zoneshould be greater, the greater the speed. of driving. The proportions ofalkali and carbon to be used in the example, about 66 parts soda ash to34 parts of charcoal of percent carbon. When using nitrogen alone heatwould be supplied by electric power alone and the theoretical energyconsumption may be estimated as about 1.5 kilowatt hours per pound ofsodium cyanid vapor. The maximum concentration of cyanid vapor,corresponding to per cent fixation of the nitrogen passed into thefurnace, would be 40 per cent by volume, assuming thevapo'r molecule tobe represented by the formula NaCN. Using air in 100 per cent excess,that is with a 50 per cent fixation of its nitrogen, if the air bepreheated to 7 50 and the gases taken off at 1200, the theoreticalelectric energy requirement, as estimated, would be reduced by about 9per cent, the proportions of soda and charcoal would be 60. :40 and theequivalent maximum concentration of cyanid vapor in the gases 28 percent. For that proportion of the cyanid removed from the furnace in themolten statean estimated saving of 20 per cent of theenergy requirementis indicated. Relying entirely upon combustion heat for .the cyanidreaction proper, using electric heat in proportion sufficient merely tobalance heat-losses, the consumption of carbon with air preheated to say750 and with the alkalized car-bon fed cold to the furnace, would beabout 2.5 lbs. per pound cyanid, the ratio of soda in the alkalizedcarbon would be 28 parts to 72 of charcoal of 90 per cent carbon and thecyanid would be in a volume concentration of about 4 per cent in thegases. Something over 3 per cent of the air nitrogen would be fixed ascyanid at the expense of 34 per cent of the calorific value of thecarbon used. In this case it may be said that 80 per cent of'the carbonis gasified by air and 20 per cent by soda. It will be seen from theforegoing that the procedure may be widely varied as desired to meetprices, scale of production, capital investment, demand for producergas, etc. As heretofore noted, with an apparatus of given size or afixed rate of gas flow, electric heating makes for a maximum time-yieldand this tends to reduce all elements of overhead cost to a minimum,

Furnaces of the types shown in Figs. 1 and 2 may be operated'discostinuously or batchsvise. In'batch operation, such a furnace maybe charged with a mixture comprising carbon and alkali (alkalizedcharcoal works well) and, brought up to about 1000 or above by electricheat. Air or nitrogen, (preferably preheated) is then passed into thefurnace and alkalize'd charcoal fed to the furnace at the same time, theproportion of alkali with the carbon being such, relative to the rate ofgas flow, that alkali is fed and cyanid formed faster than the latter isremoved from the furnace as vapor in the gases produced. As a result,cyanid accumulates in the furnace and the proportion of cyanid toresidual charcoal may be brought to any desired concentration and theoperation then discontinued. The furnace may then be cooled and thecyanized charcoal may be removed and utilized as such, or the cyanid maybe separated 100 -,varying conditions as to power costs, fuel from thecharcoal by suitable means such as leaching. Or the cyanid may bedistilled or sublimed away from the furnace while the latter is stillhot either under vacuum or by means of a circulating current of inertgas such as nitrogen, cyanid being deposited by cooling the efiluxgases. Usually the continuous method of operation is preferable.

At about 1000 the vapor tensions of most alkalies and their cyanids isfairly small so that with a moderate feed of air or nitrogen (or airenriched in oxygen), a batch of alkalized charcoal in granular or lumpform may be readily converted into cyanized carbon with a relativelysmall removal of cyanid or alkali in vapor form. With some alkalies,such as baryta, the temperature at which this is done can be higher thanwith potash or soda. The cyanized carbon will always contain someunconverted alkali; the amount depending upon temperature conditions.

Carbon being consumed in the reaction, the

proportion of cyanid and alkali (taken together) in the cyanized productis or may be greater than the proportion of equivalent alkali in theinitial alkaliz ed charcoal. When using soda as alkali, the operationmay be so managed as to yield cyanized charcoal containing a totalalkali equivalent of from 40 to 80 per cent sodium cyanid. Theproportion of cyanid (and alkali) in the product depends upon the massesof nitrogen and oxygen relative to those of the carbon and alkali. lByregulation of these proportions the said proportion of cyanid may be asdesired.

The operation of the furnaces shown in Figs. 1 and 2 may be reversed byintroducing air or nitrogen at the bottom and taking away gases at thetop; air inlets and gas outlets being simply reversed in function. Inthis event, the operation may then be so managed that all .or any partof the cyanid formed is removed from the furnace in the vapor state andrecovered from the gases. When using air, furnaces of the types of Figs.1 and 2 may be operated in a manner similar to the operation of thestructure shown in Fig. 3.

In operating'the furnace of Fig. 3, charcoal, coke, coal or othercarbonaceous matter, impregnated or mixed with soda together with fluxfor slagging the fuel ash are charged into the furnace through 26. Thefurnace being filled and the charge ignited, the materials descendslowly in countercurrent to a regulated portion of ascending gasesproduced in the hearth by the gasification of so preheated carbon withpreheatedair introduced through 20. Gases produced in the furnace arewithdraw through outlets 21 and 23 in relative proportlons definitelycontrolled in accordance with the furnace work; this control beingeffected by means of valves 31 or 4:4 and 32. Means ed to cyanid andpreheated.

mecca-r for causingthe flow of gas through the furnace are not shown butmay be either pressure applied to the inlet air line or differentialsuction applied to the respective outlet gas lines. The temperature inthe hearth and combustion zone is kept very high, ranging from 2000 C.in the immediate vicinity of the tuyeres to about 1200, usually, at thelevel of the hot gas outlets 21. Electric heat is applied by means ofcurrent passing through the electrodes 24 placed, as shown, near the topof the bosh at opposite points on the circumference. Slag and metal ifany be formed, are removed through 22 in usual ways. Cyanid is formed inthe hot zone, passes upward as vapor with the gases and out of thefurnace through 21, being recovered from the regulated portion of thefurnace gases which is caused to flow through these outlets. The cyanidcarried in the gas caused to pass up through the shaft is condensed,deposited and adsorbed in the descending alkalized carbon and the cyanidfrom the gas more or less reverts to oxid and carbonate in the coolerportion of the shaft. Thus the sensible heat of the CO and N and alsothe latent heat of vaporization of cyanid, and to a greater or lessextent the sensible heat and the energy of reversion of the cyanid tooxid and carbonate are applied to the preheating of the soda and carbonand to the work of cyanid formation, so that the shaft delivers to thecombustion zone alkali and carbon, with the alkali already to a greateror less extent deoxidized or convert- The proportion of the total workwhich is done in the shaft depends upon the regulation of the furnaceoperation, the principles of which may be illustrated as follows':Thework of converting cold carbonte, carbon and nitrogen to cyanid vaporand CO at 1200 has been hereinbefore estimated at 138060 calories permolecule NaCN. Under the coun-' tercurrent stated action in the shaft ofthe furnace, the sensible heat of the CO formed in the cyanid reactionis recuperated by the descending alkali and carbon and the item of 13400calories per molecule NaCN estimated as the sensible heat of 1:}molecules CO at 1200 may be left out of the calculation, leaving thetotal heat required at 124660 calorles per molecule NaCN or 2544 thermalunits per pound cyanid. For purposes of illustration this work may bedivided into three steps as follows (1) Conversion of carbonate .to oxidin the reaction, Na,CO -|-C:Na.,O+2CO, and preheating Na O+3C to 1200;

(2) Conversion at 1200 of liquid oxid to liquid cyanid in the reaction,Na O+3C+ N,':2NaCN+CO (3) vaporization of liquid cyanid at 1200 Thechemical energy involved in (1) may be taken as 114480 calories and in(2) as per molecule N aCN With the molecular specific heat of 13(1+0.00039 t) the sensible heat ofNa O at 1200 maybe estimated as about23000 calories; the molecular heat of fusion is estimated at 4500calories; and the molecular figures may be taken as about the same forcyanid. The heat in carbon at 1200 is 5832 calories'per gram-atom. Hencethe'work involved in the three steps nay'be estimated to be: i

(1) 79238 calories per molecule or 1617 thermal units per pound cyanid.

(2) 15422 calories per molecule or 315 thermal units per pound cyanid.(3) 30000 calories per molecule or 612 thermal units per I I poundcyanid.

Total, 124660 2544 thermal units per pound cyanid. The relativeproportions of the gas from the combustion zone caused to leave thefurnace through hot gas outlet (21) of Fig. 3, and top gas outlet (23)respectlvely may be so adjusted that any desired proportion of the workinvolved in steps (1) and (2) may be done in the shaft. It is usuallyeconomical so to manage the operation that electric energy is utilizedin quantity only sufiicient to compensate vheat losses; and to causesufiicient gas carrying cyanid to pass I so upthrough the shaft in ordertoconvert all descending alkali to liquid cyanid preheated to about1200; in other 7 words to;

' complete steps and (2) in the shaft leaving only step (3) or itsequivalent to .be done in the combustion zone. So working, carbonis'needed in the hearth to be gasified with air atsay 750 to theextentof about 0.32 pound per pound of vaporized I cyanid. Thecorresponding volume concen- 40 tration of cyanid vapor is about 20 percent of the mixed gases. About 55 per cent of these gases, caused topass up through the shaft where they contact with descendin alkali andcarbon, by virtue oftheir sensible heat and latent and potential energydeveloped in the condensation and partial cooling and reversion ofcyanid and deposition of carbon is suflicient to complete the conversionto cyanid of sufficient alkali (which should be charged with the carbon)to replace the cyanid removed from the furnace in 45. per cent of thegases produced in the combustion zone. Such a proportionof said gasesmay bewithdrawn through the hot gas outlets 21. The consumption of car-'bon in the gasification with air in the combustion zone is thus about0.72 pound per pound of cyanid recovered from the per cent of the gasesand 0.49 pound carbon is consumed in the cyaniding reaction; butfrom thepercent of the gas going up through the shaft carbon is deposited in thedecomposition of'CO' and with full (levelopment in thisiway of thelatent energy of from he combust on zon the carbon s deposited mayamount to 0.2 pound per pound of recovered cyanid, leaving the netcarbon requirement about one pound per ratio in the top gas, increasingthe proportion of hot gas withdrawn with rise of top temperature andfall of CO ratio and vice versa I may thus hold the top temperature andCO ratio at a desired point, corresponding to a desired degree ofutilization inthe furnace of the fuel energy. Beyond a certain limit,the greater the .proportion of hot gas taken from the furnace at 21, thesmaller the proportion of the fuel energy utilized in the furnace andhence, the application of electric heat. remaining suflicient to balancelosses, the greater the consumption of carbon per pound cyanid. Forexample, with a hot gas withdrawal of about 58 per cent with 42 .percent of the gases the shaft), the work devolving upon the combustionzone is about the equivalent of steps (2) and With electric heatcompensating heat losses in the combustion zone, this work-requires the,gasification of. about 0.49 pound carbon (preheated, to- 1200) with airat 750. An equatio f action might be written?) or the re-' I bon, sodiumoxid and air in these proper; tions (the carbon'andsoda being preheatedto 1200 and the air to 750) absorbsfnog heat and it follows that withair in-greater proportions, or if the materials be more;

highly preheated the reaction is exothermic. Putting it in another way:The theoretical temperature of the gasification of preheated carbon, 42per cent by'preheated soda and 58 per cent by air preheated to 750 isabout 1200. Some 13 per cent of-the air, nitro: gen is fixed as cyanidvapor in a concentration of about 14 per cent of the products of thegasificatiom With cyanid recovered from 58 per cent (by volume) of theseprodnets and the other 42 per cent being utilized for preheating moresoda and carbon, the total consumption of carbon is about 1.17 pound perpound cyanid produced. The proportions of soda and fuel (90% carbon)charged into the furnace should in this case be a t 5: 5. It may e notedthat in a ca scowm any case these proportions should be carefullyadjusted in correlation with the volume of hot gas withdrawn at 21 andthe concentration of cyanid therein. Carbon may be introduced into thehot zone of the furnace in the form of liquid or gaseous hydrocarbons involume so regulated as to adjust the proportions of alkali and carbon asdesired. By increasing the electric energy applied the consumption ofcarbon may be reduced and a greater proportion of gas may be withdrawnthrough the hot gas outlet without reducing the concentration of cyanidin such gas. The regulation of the furnace operation is a matter .ofcoordinating the volume of hot gas withdrawn with the blast temperatureand with the application of electric power, in conjunction with theproportions of alkali and carbon.

In applying the present invention to the general problem of nitrogenfixation, cyanid made as described is hydrolyzed to ammonia withrecovery of alkali and this alkali may be returned to the furnace to beagain cyanided. It is advantageous to practise the invention in a blastfurnace in simultaneously producing cyanid and iron or action zone byaid of heat supplied by electrical means.

2. The process of making cyanids which comprises feeding air, alkali andcarbon into a reaction chamber in which is maintained by aid of heatsupplied by electrical means a mass of cyanized carbon at a temperatureabove 1000 C.

3. The process of makin cyanids which comprises feeding air, alkali andcarbon into a reaction chamber in which is maintained by aid of heatsupplied by electrical means a mass of cyanized carbon at a temperatureabove 1000 C. and removing cyanid from the sphere of reaction.

4. The process of making cyanids which comprises downwardly feeding air,alkali and carbon into a reaction chamber in which is maintained by aidof heat supplied by electrical means a mass of cyanized carbon at atemperature above 1000 C. and removing cyanid from the sphere ofreaction.

5. The process of making cyanids which comprises downwardly feeding air,alkali and carbon into a reaction chamber in which is maintained by aidof heat supplied by electrical means a mass of cyanized carbon at atemperature above 1000 C. and removing cyanid from the bottom of saidreaction chamber.

6. The process of making cyanid which comprises contacting a mass ofalkalizcd carbon heated electrically to a cyanid forming temperaturewith a mass of nitrogen and oxygen so regulated that the proportion ofcyanid and alkali in the resulting cyanized carbon is greater than theproportion of equivalent alkali in the initial alkalizcd carbon.

7. A process of making cyanid which comprises contacting alkali vaporand nitrogen with cyanized carbon maintained at a temperature above 1000C. with the aid of heat supplied by electrical means.

8. A process of making cyanid which comprises feeding alkali, carbon andnitrogen into a reaction chamber to react with a mass of cyanid thereinmaintained at a temperature above 1000 C, removing cyanid laden gasestherefrom and quickly cooling said gases to deposit cyanid substantiallywithout reversion.

9. A process of making cyanid which comprises passing nitrogen intocontact with alkali and carbon maintained at a cyanid formingtemperature and quickly cooling resulting gases to deposit cyanidtherefrom substantially without reversion.

10. A process of making sodium cyanid which comprises heating togetherto a cyanid-vapor-forming temperature sodium carbonate, carbon andnitrogen and quickly cooling resulting gases to deposit sodium cyanidsubstantially without reversion.

11. A process of making cyanid which comprises contacting nitrogen withalkali and carbon at a cyanid forming temperature maintained with aid ofheat supplied to the sphere of reaction by means of electrical currentsinduced therein or in proximity thereto.

12. In nitrogen fixation the process which comprises contacting airpreheated to substantially above 500 C, with alkalized and cyanizedcharcoal maintained at about 1200" C, by aid of heat supplied byelectrical means.

13. In the manufacture of cyanids the process which comprises contactingat a temperature above 1000 C, preheated carbon and alkali under gasproducing conditions with preheated air. recovering cyanid from aregulated proportion of the gases produced while preheating carbon andalkali with another regulated portion of said gases, and maintaining thetemperature and a substantial concentration of cyanid vapor in the gasesby aid 'of heat supplied by electrical means.

14. In the manufacture of sodium cyanid the process which comprisescontacting at cyanid-vapor-forming temperatures preheated carbon andsoda under gas producing conditions with preheated air, recoveringsodium cyanid from a regulated proportion of the gases produced whilepreheating carbon and soda with another regulated 'portion of saidgases, and maintainmg the temperature and a substantial concentration ofcyanid vapor in thegases by aid of heat supplied by electrical means. lI

15. In cyanid making the process of cooling hot cyanid laden gases anddepositing cyanid therefrom substantially without reversion whichcomprises leading such gases into a cooling chamber in which arelatively large mass of cooled gas is maintained.

16. The process of making sodium cyanid which comprises feedingnitrogen, soda and carbon into a reaction chamber in which is maintainedby aid of heat supplied by electrical means a mass of cyanized carbon ata temperature above 1000 C.

17. In making cyanid vapor by heating together in a shaft furnacecarbon, alkali and'air in the presence of cyanid, the proccess ofproviding in the hot zone a volume of heat available for work at cyanidforming temperatures which comprises reinforcing by heat electricallysupplied the heat developed by CO formation from preheated air; andcarbon preheated by counter-current contact in the shaft with aregulated prof I portion of cyanid-laden gases previously produced.

18. In the fixation in a blast furnace of nitrogen as cyanid vapor bygasifying carbon with soda and air at temperatures above 1000 C., theprocess of making the cyanid forming reaction exothermic which comprisesregulating the relative proportions of alkali and carbon charged intothe furnace in correlation with the blast heat and preheating saidcarbon and soda by counter current contact in the furnace shaft with a.regulated proportion of the cyanid-laden gases produced in the hearth,cyanid being recovered by quickly cooling another portion of such gasesWithdrawn from the furnace 'at a level of high temperature.

7 19. In making cyanid from carbon, alkali and nitrogen 'in the presenceof preformed cyanid in a shaft furnace heated by electrical means, theprocess of controlling the heat economy of the operation which comprisespreheating the carbon and alkali descending through the furnace shaft tothe electrically heated zone by counter current contact with a regulatedcyanid-laden gases.

In testimony whereof, I have hereunto affixed 111 Si ature.

y K. P. MoELROY.

quantity of ascending

